1. Field of the Invention
The present invention relates to a lithography system and a method of manufacturing devices using the lithography system. The lithography system and method of manufacturing devices using the lithography system are successfully adaptable to a method and system for manufacturing microscopic lines and spaces, or more particularly, to a method and system for manufacturing semiconductor devices using a diffraction grating. The semiconductor devices include optical devices, a semiconductor laser, and devices to be integrated into a semiconductor integrated circuit.
2. Description of the Related Art
According to a first method of forming a pattern of lines and spaces that has been adopted in the past, two-beam interference fringes are, as shown in FIG. 1, produced on a substrate to which a photosensitive agent is applied. The substrate is developed after being exposed. A pattern of lines and spaces is formed using the photosensitive agent. The substrate is then etched, while being masked with the pattern of lines and spaces formed with the photosensitive agent. The pattern of lines and spaces is thus drawn on the substrate.
Referring to FIG. 1, light emanating from a coherent light source such as a laser is bifurcated by a beam splitter 101, reflected by mirrors 102 and 103, and crossed on a substrate 104. At this time, interference fringes, or in other words, a pattern of lines and spaces is formed in a two-beam crossing area 105. Assuming that an angle of incidence of the light beams is .theta. and a wavelength provided by the coherent light source is .lambda., the pitch P between adjoining lines and spaces of the pattern is expressed as follows: EQU P=.lambda./(2 sin .theta.)
For example, when a He--Cd laser providing a wavelength of .lambda.=325 nm is used as the coherent light source, and the angle of incidence .theta. is 60.degree., a pattern of lines and spaces having a pitch P=0.188 um (0.1 um or less between adjoining lines) can be drawn.
The foregoing two-beam interference fringes-based lithography method has the features described below. One of the features lies in that the cost of manufacturing is lower than that required by step-and-repeat photolithography method with demagnification. According to the step-and-repeat photolithography method with demagnification, a pattern is drawn on a mask using an electron-beam plotter and then projected on a substrate using a step-and-repeat photolithography system with demagnification. Another feature lies in that it is easier to draw a pattern with a pitch between adjoining lines and spaces set at 0.15 um or less than it is according to the step-and-repeat photolithography method with demagnification. The step-and-repeat photolithography method with demagnification adopts an excimer laser, which is currently a mainstream laser, as a light source. Another feature is a higher resolution than that offered by the step-and-repeat photolithography method with demagnification.
However, for example, a semiconductor device can be produced by overlaying numerous layers of patterns of circuits on a substrate (wafer). For exposing the wafer in order to form patterns of circuits of the second and subsequent layers, each pattern of the circuits to be formed must be highly precisely aligned with each shot location on the wafer. At each shot location, a pattern of circuits has already been formed. No practical method of directly controlling a location to be exposed to interference fringes has been implemented in existing interference fringes-based lithography systems. The interference fringes-based lithography systems must be further innovated so that they can be used to manufacture devices to be integrated into a semiconductor integrated circuit. For manufacturing the devices, patterns of circuits must be overlaid successively.